> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/welcome/content-delivery-network/domain-management/access-control/ua-restrictions.md).

# UA Restrictions

Zenlayer CDN allows you to configure a User-Agent blacklist identify and filter requests. This way, you can restrict access to CDN resources and improve service security.

User-Agent is an HTTP header. It contains the information about the client that makes the request, including the operating system (OS), OS version, browser, and browser version.

User-Agent blacklist: Requests whose User-Agent header has a value in the blacklist are rejected. The HTTP 403 status code is returned to the client.

<div align="left"><figure><img src="/files/jfdwqy0vYvqdKoI1ISp5" alt="" width="375"><figcaption></figcaption></figure></div>

### Block List

Expected result: Access to the above fields in the UA will be blocked.